How to Test a Diesel Fire Pump

Fire pumps are the heart of fire suppression systems. They provide high rates of water flow at increasing pressure to quickly and efficiently suppress a fire. They are the workhorses of any building. As a result, these pumps are subject to intense stress and must be tested on a regular basis to ensure they will operate as needed in an emergency situation. Unlike electric fire pumps, which have their motors and other electrical components located inside the pump, diesel fire pumps are able to be separated from their engines. This allows for more testing, maintenance and other procedures that are not possible with electric fire pumps.

The NFPA 20 standards require that the diesel engine fire pump be tested annually to confirm its ability to perform its intended function during an emergency. During the test, the diesel engine should be able to deliver a minimum of two-thirds of its rated capacity at 100 percent shutoff head. The fire pump is also required to have a minimum of 120 gallons of fuel available for operation.

If these requirements are not met, the system could fail to operate during a fire and leave your facility without a means of fire suppression. This is why it is important to understand how the diesel fire pump operates and the testing protocol that is required.

A common issue with stand-by diesel fire pumps is that they can be damaged by not having enough coolant flow to the engine heat exchanger from the fire line piping. The engine needs this constant flow in order to remain cool and not overheat. Failure to maintain this flow is a primary cause of damage to the Diesel engine fire pump during an annual test.

The solution to this issue is to install a manual isolation valve on the supply and discharge piping. This will prevent the fire pump from attempting to start when there is not sufficient cooling water for it to do so. Additionally, it is critical to make sure that the fire pump room temperature is maintained at 40 degrees Fahrenheit or higher in order to prevent degrading the batteries and gelling of the diesel fuel located in the tank.

It is also necessary to have a thermostatically controlled block heater on the diesel fire pump to maintain it at its proper operating temperature. Hotstart manufactures a range of thermostatically controlled heaters that are compatible with most diesel fire pumps.

It is also important to check that the nozzles and valves in the fire pump are properly sized for the maximum capacity of the diesel fire pump and that they are rated for use at that maximum. Finally, the UL or FM approved driver must be sized to meet the full horsepower demands of the fire pump and the NFPA 20 standards. Failure to do so will lead to premature failure of the driver and the fire pump.

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